NUTRIG: novel techniques for pure, efficient and scalable autonomous radio detection of high energy neutrinos and cosmic rays

经过一个多世纪的理论和实验研究，超高能量宇宙射线（宇宙中能量最高的粒子，有时能量超过10^20 eV）的起源仍然是一个谜。对能量超过10^17 eV的宇宙中微子的探测可能允许确定它们的来源。这些难以捉摸的信使将是研究宇宙中剧烈现象的宝贵工具，特别是如果它们的观测与引力波、伽马射线或其他波长的电磁波相结合的话。迄今为止，对这些超高能量中微子进行观测的最有希望和最成熟的实验建议之一是部署覆盖100,000 km^2或更大区域的巨型射电阵列，例如GRAND项目特别提出的那样。这种射电阵列将探测到目标宇宙粒子（中微子或宇宙射线），这要归功于它们在大气中的相互作用所引起的粒子阵雨的瞬态射电发射。这种非常经济实惠的无线电技术完全适用于实现在这些极端能量下收集稀有粒子所需的巨大探测区域。然而，一个尚未解决的主要挑战在于实现自主在线拒绝背景无线电瞬变（与大量来源相关，如电力线，地球上的无线电通信，飞机，雷暴等），即使在遥远的沙漠地区，如GRAND所针对的地区，也会产生比空气阵雨高得多的无线电脉冲率。我们建议与NUTRIG项目一起解决这一具体问题，通过开发一种高效和纯粹的触发系统，可扩展到巨大的区域，这将允许通过不同于背景信号的特定特征选择与宇宙粒子相关的无线电瞬变。这个独特的项目由我们的德法合作开发，将使用GP300实验在实际条件下进行验证，GP300实验是GRAND项目的探路者。我们两个团队在宇宙射线和空气阵雨自主无线电探测领域的专家的综合专业知识，使我们处于解决这一关键问题的完美位置，并将为未来的巨型宇宙粒子探测器铺平道路。

The origin of ultra-high energy cosmic rays - the most energetic particles in the Universe, sometimes exceeding energies of 10^20 eV - is still a mystery, after more than a century of theoretical and experimental research. Detection of cosmic neutrinos beyond energies of 10^17 eV may allow to identify their source. These elusive messengers would be precious tools to study violent phenomena in the Universe, especially if their observation is combined with that of gravitational waves, gamma rays or electromagnetic waves at other wavelengths. One of the most promising and mature experiment proposals so far for the observation of these ultra-high energy neutrinos consists in deploying giant radio arrays covering areas of 100,000 km^2 or beyond, such as proposed by the GRAND project in particular. Such radio arrays would detect the targeted cosmic particles (neutrinos or cosmic rays) thanks to the transient radio emission of particle showers induced by their interaction in the atmosphere. The very affordable radio technique is perfectly adapted to achieve the gigantic detection areas needed to collect the rare particles observed at these extreme energies. Yet, a major unsolved challenge lies in the realization of an autonomous online rejection of background radio transients (associated with a wealth of sources such as power lines, radio communication on Earth, air planes, thunderstorms, etc.) which induce - even in remote, desertic areas such as the one targeted by GRAND - a much higher rate of radio pulses than air showers. We propose with the NUTRIG project to address this specific issue by developing an efficient and pure triggering system, scalable to giant areas, which will allow selecting radio transients associated with cosmic particles through specific signatures which differ from those of background signals. This unique project, developed by our German-French collaboration, will be validated in real conditions using the GP300 experiment, a pathfinder for the GRAND project. The combined expertise of our two teams, experts in the field of cosmic rays and autonomous radio detection of air showers, puts us in a perfect position to address this key issue, and will pave the way for future giant detectors of cosmic particles.